In general, the present invention relates to security control systems and more particularly to an electronic permutation lock which opens in response to a predetermined combination code, where the code may be entered for example by manually operated electromechanical switches.
Electronic permutation or combination locks are in general known and the utility thereof is widely accepted. Many of the electronic combination locks heretofore proposed have merely substituted the electronic functions for the mechanical tumbler parts of the well-known conventional combination lock. Thus such previous electronic systems merely provide an electronic counterpart to the mechanical combination lock and in general provide substantially the same security functions which have long been within the capability of the mechanical lock.
It is a general object of the present invention to provide an electronic permutation or combination security control system having far greater versatility and flexibility than is capable of mechanical devices. For example, it may be desirable in certain security installations to change the length or complexity of the entry code necessary for operating the lock. During periods of frequent use of the code entry such as during the daytime, it may be desirable to provide a short two, three or four digit entry code, whereas other periods such as at nighttime will demand a higher security entry code of five or more digits.
Also, it is many times desirable to permit changing of the entry code. For example, some security systems may require the code to be changed periodically to minimize the risk of the code being leaked to an unauthorized person. In other situations, two or more different codes may be provided for use during different times of the day. One code for use during daytime hours might be known to all authorized personnel, whereas a nighttime code may be known only to the attendants or night watchmen.
Some previously proposed electronic combination locks have recognized and used certain security features particularly within the capabilities of the electronic art. For example, many systems provide for the detection of errors occurring during entry of a combination code and provide for some form of disablement of the lock circuitry in response thereto. However, it would be desirable to provide in accordance with the aforementioned general objective of the present invention to provide for not only detecting errors, but to permit a selectable number of errors to occur prior to disablement of the lock. This would permit the control system to be set according to the desired security level. For a high security situation, the number of errors permitted prior to disablement would be set to zero, 1 or 2 for example. On the other hand, a low level of security may permit the occurrence of a plurlity of errors before opening of the lock is foreclosed, thus permitting ease of access by low security personnel or during low security periods. Additionally, the error number setting would be useful in introducing the system to security employees, with a high error setting being used initially until they have become familiar with the system and/or a code number, and thereafter reducing the error setting to a low level for higher security.
The duration of the lock disablement following a threshold error count is desirably adjustable to accommodate the particular security requirements. For a low security system, the disablement interval or penalty time may be relatively short to provide a compromise between preventing unauthorized entry and yet affording eventual access to authorized personnel who is merely careless in entering the proper code. On the other hand, a high security system may demand a much longer penalty time to preclude the breaking of the combination code by an authorized person having sufficient time to try each of the possible permutations. Thus a penalty time setting would be a desirable feature to have in a sophisticated, versatile security system.
Typically, the output of the electronic combination lock is employed to drive some form of electromagnetic release or solenoid lock. The time interval during which the lock is driven to the open condition can be a critical characteristic of the system. For example, a solenoid lock which is driven to the open condition and maintained there for an extended length of time is undesirable because unauthorized personnel may sneak through the security access following entry of an authorized person. To minimize this possibility, it would be desirable to provide a variable, setable time interval during which the solenoid lock is maintained open. Thus, depending upon the situation, the lock open time may be set for one or two seconds on up to several seconds depending upon the expected time required for the authorized personnel to enter the code and open the door, safe, or other secured area. This entry time may vary depending upon the installation, and thus the flexibility provided by the variable, setable lock open time would be advantageous.
Although the code combination provides a great deal of security against unauthorized entry, it is nevertheless desirable in some systems to provide in addition thereto a time lock feature. In such case, the security lock is disabled for a predetermined, set time, and only after expiration of this time will the circuit respond to the entry of the proper code to open the lock. Time locks are desirable in many installations including bank vaults, computer rooms, and in general in any security area which is to be locked up during certain time frames such as overnight. Although time locks are in general known, they have not heretofore been provided in the most advantageous and compatible form for use with an electronic permutation lock.
Similarly, it is well-known to provide some form of controlled, electrical power supply for operating the solenoid or other electromagnetic locks responsive to the electronic combination circuitry. However again, these known circuits have not been provided in a form which is most advantageous for use in combination with a sophisticated electronic control circuit. For example, even though the electronic control circuitry itself is operable with very low power requirements, even permitting the use of small emergency batteries, previously proposed solenoid driver circuits have required a great deal of power and are many times incapable of being operated by a small battery. This, of course, restricts the otherwise available flexibility of the electronic control. Accordingly, it would be desirable to provide a solenoid or latch driver circuit which is more compatible to a sophisticated electronic permutation lock, and more particularly to provide such a driver circuit having a relatively low electrical power requirement.
In accordance with the present invention the foregoing features are not only recognized as desirable characteristics of a sophisticatd, versatile security control system, moreover all of these features are constructed in a manner which is inherently reliable and is capable of being mass manufactured at a relatively low per unit cost. For example, in order to reduce the overall cost of the system, certain common circuit components are used for a plurality of different functions thereby reducing the number of required components and simplifying the production assembly.
These and other objects, advantages and features of the electronic permutation lock and control system in accordance with the present invention will become apparent to those skilled in the art from a consideration of the following detailed description of a few particular embodiments thereof. Reference will be made to the appended sheets of drawings in which: